Gearbox control system

ABSTRACT

In a gearbox control system ( 8 ) for detecting systematic errors and long-term changes, the behavior of a real gearbox ( 1 ) is compared to the behavior of an ideal gearbox ( 7 ), which is implemented in the form of a gearbox model in the gearbox control system ( 8 ).

[0001] The invention concerns a gearbox control system of the type defined more clearly in the preamble of claim 1.

[0002] Gearboxes can be individually adapted to different types of vehicles with the aid of gearbox control systems. In doing so, the gearbox control system makes possible the integration of functions that are relevant to comfort, safety, and service. The shifting comfort is generally in the foreground, even though it is directly felt by the driver. Other important functions concern the shift point control, safety, and diagnosis. Shifting comfort is still quite important. An excellent shifting comfort, which remains constant during the entire service life of the gearbox, is the main duty of the gearbox control system.

[0003] The shifting comfort is influenced by a variety of parameters which are described in the ATZ Automobiltechnische Zeitschrift 93 (1991). By means of an optimal combination of friction elements, such as multi-plate clutches and brake band and the corresponding gearbox oil, a constant friction value level can be achieved. The shifting pressure of the multi-plate clutches or of the brake band is controlled in dependence upon parameters such as gear stage, engine speed, throttle flap angle for thrust-traction recognition, gearbox output speed, engine speed, gearbox temperature, and engine temperature in such a way that a uniform shifting operation always takes place. Furthermore, an adaptive pressure control takes place; that is, the deviations from specific parameters are automatically corrected during the operation time of the gearbox.

[0004] For this reason, the response times or gliding times are permanently measured and average response times are determined from several shifting operations. If there is a deviation of the average response time from desired, response times dependent from the load and engine speed, the clutch pressure is changed until the desired response time is reached.

[0005] In this solution, which is known from the state of the art, it is not possible to detect, however, and correct systematic errors and long-term changes, since gearbox transmission errors cannot be detected.

[0006] It is an object of the invention to present a gearbox control system which can detect gearbox transmission errors and thus can compensate for systematic errors and long-term changes.

[0007] The basic object of the invention is attained by means of a gearbox control system of the type described above, which also has the characteristic features of the independent claim.

[0008] Comparisons between the real behavior of a gearbox and the behavior of an ideal reference gearbox take place to attain the objective. This reference gearbox is implemented in the gearbox control system in the form of a gearbox model. For this purpose, the calculated shifting pressure is sent by means of a pressure control valve to the gearbox and, at the same time, fed to the reference gearbox in the gearbox control system. During the shifting operation, the gearbox control system continuously measures the previously defined parameters of the gearbox and compares them to the corresponding parameters of the reference gearbox. The gearbox control system determines the deviations between the parameters of the real gearbox and the reference gearbox and calculates a pressure correction value therefrom which is taken into consideration during the next shifting operation, and is superimposed on the real gearbox in such a way the behavior of the real gearbox and the reference gearbox converge. This operation is repeated for each further shifting operation until the deviations between the real gearbox and the reference gearbox have been reduced to a minimum. In an ideal case, a correspondence between the real gearbox and the reference gearbox results. The adaptation of the real gearbox and the reference gearbox can take place, to a great extent, independently from the operating condition. All the occurring known systematic influencing variables can be integrated in the reference gearbox and can thus be taken into account during operation. For example, load conditions, shift points, accelerations, and temperatures can be incorporated in the reference gearbox. The adaptation of the real gearbox and reference gearbox can also take place independently of the gradient of the shifting pressure. The shifting pressure can, therefore, also include any desired components of a pressure control or a superimposed pressure control, without this having an effect on the adaptation of the real gearbox to the reference gearbox.

[0009] An exemplary design of the invention will be described in principle with reference to the FIGURE.

[0010] The single FIGURE shows a schematic of a gearbox control system of the invention.

[0011] A real gearbox 1 is characterized by the actual condition which is defined by parameters, such as, the input speed 2 and the input torque 3 as well as the output speed 4 and the output torque 5. Disturbance variables 6 are added to them, which influence the real gearbox. A desired condition is determined from the input speed 2 and the input torque 3 in an ideal reference gearbox 7 which is integrated, as a gearbox model, in the gearbox control system 8. From the input speed 2 and input torque 3 parameters, a shifting pressure 9 is calculated, which is further processed with the deviation from the actual condition and desired condition in the gearbox control system 8 to a pressure correction value 10. In addition, with the aid of an adaptation logarithm 11 error functions can be integrated in the calculation of the pressure correction value 10.

[0012] Reference Numerals

[0013]1 real gearbox

[0014]2 input speed

[0015]3 input torque

[0016]4 output speed

[0017]5 output torque

[0018]6 disturbance variables

[0019]7 ideal reference gearbox

[0020]8 gearbox control system

[0021]9 calculated shifting pressure

[0022]10 pressure correction value

[0023]11 adaptation algorithm 

1. A gearbox control system (8) for detecting systematic errors and long-term changes, wherein the behavior of a real gearbox (1) is compared to the behavior of an ideal reference gearbox (7), which is implemented in the form of a gearbox model in the gearbox control system (8).
 2. The gearbox control system (8) of claim 1, wherein a calculated shifting pressure (9) is sent to the real gearbox (1) and at the same time fed to the reference gearbox (7) in the gearbox control system (8).
 3. The gearbox control system (8) of claim 1 or 2, wherein the gearbox control system (8) measures continuously the previously defined parameters of the gearbox and compares them to the corresponding parameters of the reference gearbox during the shifting operation.
 4. The gearbox control system (8) of one of the previous claims, wherein the deviations between the parameters of the real gearbox and the reference gearbox are determined and a pressure correction value (10) is calculated therefrom, which is taken into account in the next shifting operation, and which is superimposed on the shifting pressure of the real gearbox in such a way that the properties of the real gearbox (1) and the ideal reference gearbox (7) converge.
 5. The gearbox control system (8) of one of the previous claims, wherein the adaptation of the real gearbox (1) and the ideal reference gearbox (7) can take place to a great extent independently from the operating condition and from the gradient of the shifting pressure. 